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Biomedical subjects

S Siegler

Publications and source records attributed to S Siegler.

27 records · Page 2Linked to original sources
PubMed1991

Objective identification of ankle equinus deformity and resulting contracture.

A quantitative diagnostic technique is described for identifying contracture at the ankle joint in patients with equinus deformity, hence addressing the shortcoming of the conventional clinical diagnostic procedure. To gain a better understanding of how contracture contributes to equinus deformity, a study was designed that compared the torque about the ankle joint before and after administering a tibial nerve block to equinus patients and to a control group. Functional equinus, manifested by walking and early heel rise, is defined as inadequate dorsiflexion for normal gait. The ability to accurately identify an equinus condition, and contracture as the contributing factor in equinus deformity, has important implications for the type of treatment prescribed and the evaluation of treatment effectiveness.

Adolescent↗
PubMed1990

The effect of damage to the lateral collateral ligaments on the mechanical characteristics of the ankle joint--an in-vitro study.

Injuries to the lateral collateral ligaments of the ankle joint are among the most frequently occurring injuries at the lower limb. The present study was conducted for the purpose of establishing the basis for the development of a quantitative diagnostic procedure for such injuries. To achieve this goal, the effect of four types of ligament injuries on the three-dimensional mechanical characteristics of the ankle were investigated. These types of injuries consisted of: 1) isolated tear of the anterior talofibular ligament; 2) isolated tear of the calcaneofibular ligament; 3) isolated tear of the posterior talofibular ligament; and 4) combined tear of both the anterior talofibular ligament and the calcaneofibular ligament. The experiments were conducted on 31 amputated lower limbs and consisted of comparing the three-dimensional load-displacement and flexibility characteristics of the ankle joint prior to and following sectioning of selected ligaments. The experimental and analytical procedures used to derive these characteristics was developed previously by the authors. From the results of this study it was concluded that the three-dimensional flexibility characteristics of the ankle joint are strongly influenced by damage to the lateral collateral ligaments. Furthermore, it was found that each type of ligament injury produced unique and identifiably changes in the flexibility characteristics of the ankle. These unique changes, which are described in detail in this paper, can be used to discriminate between the different types of ligament injuries. Consequently, it was concluded that it is feasible to develop a quantitative diagnostic procedure for ankle ligament injuries based on the effect of the injury on the flexibility characteristics of the ankle.

Aged↗
PubMed1988

The three-dimensional kinematics and flexibility characteristics of the human ankle and subtalar joints--Part I: Kinematics.

The in-vitro, three dimensional kinematic characteristics of the human ankle and subtalar joint were investigated in this study. The main goals of this investigation were: 1) To determine the range of motion of the foot-shank complex and the associated range of motion of the ankle and subtalar joints; 2) To determine the kinematic coupling characteristics of the foot-shank complex, and 3) To identify the relationship between movements at the ankle and subtalar joints and the resulting motion produced between the foot and the shank. The tests were conducted on fifteen fresh amputated lower limbs and consisted of incrementally displacing the foot with respect to the shank while the motion of the articulating bones was measured through a three dimensional position data acquisition system. The kinematic analysis was based on the helical axis parameters describing the incremental displacements between any two of the three articulating bones and on a joint coordinate system used to describe the relative position between the bones. From the results of this investigation it was concluded that: 1) The range of motion of the foot-shank complex in any direction (dorsiflexion/plantarflexion, inversion/eversion and internal rotation/external rotation) is larger than that of either the ankle joint or the subtalar joint.; 2) Large kinematic coupling values are present at the foot-shank complex in inversion/eversion and in internal rotation/external rotation. However, only a slight amount of coupling was observed to occur in dorsiflexion/plantarflexion.; 3) Neither the ankle joint nor the subtalar joint are acting as ideal hinge joints with a fixed axis of rotation.; 4) Motion of the foot-shank complex in any direction is the result of rotations at both the ankle and the subtalar joints. However, the contribution of the ankle joint to dorsiflexion/plantarflexion of the foot-shank complex is larger than that of the subtalar joint and the contribution of the subtalar joint to inversion/eversion is larger than that of the ankle joint.; 5) The ankle and the subtalar joints have an approximately equal contribution to internal rotation/external rotation movements of the foot-shank complex.

Algorithms↗
PubMed1988

The three-dimensional kinematics and flexibility characteristics of the human ankle and subtalar joint--Part II: Flexibility characteristics.

The objective of the present study was to investigate the in-vitro, coupled, three-dimensional load-displacement and flexibility characteristics of the human ankle joint complex consisting of the talocrural and the talocalcaneal joints and to determine the effects that sectioning of the anterior talofibular ligament has on these characteristics. Similar to other anatomical joints such as the knee and the intervertebral joint, the ankle joint complex was found to exhibit highly nonlinear load-displacement characteristics with the angular displacement approaching asymptotic values as the external load was increased. Therefore, a procedure of incremental linearization was used to derive the flexibility characteristics of this structure. According to this procedure, external loads were applied to the calcaneus in small increments and its resulting three dimensional displacements were recorded. The incremental flexibility coefficients were then derived by assuming linear load-displacement relationship for each increment. From the results obtained from fifteen human ankle specimens, it was evident that the ankle joint complex exhibit highly coupled flexibility and load-displacement characteristics. It was further concluded that the ankle joint complex is the most flexible in the neighborhood of the unloaded, neutral position and that all the flexibility coefficients of the structure decrease rapidly toward the extremes of the range of motion. Rupture of the anterior talofibular ligament was found to have a significant effect on the load-displacement and flexibility characteristics of the ankle joint complex. This effect was manifested as a change in the load-displacement characteristics and a large increase in the flexibility coefficients primarily in those corresponding to rotations in the transverse and the coronal plane. The results of the present study can provide the necessary data base for the development of quantitative diagnostic technique for identifying the site and the extent of injury to the collateral ligaments of the ankle.

Ankle Injuries↗
PubMed1988

The mechanical characteristics of the collateral ligaments of the human ankle joint.

In the present study, the tensile mechanical properties of all of the collateral ligaments of the human ankle joint were determined, in vitro, from tensile tests conducted on 120 ligaments obtained from 20 fresh lower limbs. The ultimate load of the lateral collateral ligaments increased in an anteroposterior sequence, with the anterior fibulotalar ligament less than the fibulocalcaneal ligament and less than the posterior fibulotalar ligament. For the medial collateral ligaments, the increasing order of ultimate load was found to be tibiocalcaneal ligament, tibionavicular ligament, tibiospring ligament, posterior tibiotalar ligament. The posterior tibiotalar ligament and tibiospring ligament, so frequently neglected in the anatomical and orthopaedic literature, demonstrated the highest yield force and ultimate load of all of the collateral ligaments of the ankle. Additionally, the tibiospring ligament showed high yield and ultimate elongation properties probably related to its distal attachment to the spring ligament. The fibulocalcaneal ligament was found to have high linear elastic modulus suggesting some type of unique material properties or internal fiber organization. Knowledge of the mechanical characteristics of the ligaments of the ankle joint contributes to an understanding of their normal function, pathomechanics of injury, and their optimal surgical reparative procedure and reconstructive material. A knowledge of the normal mechanical properties of the ankle ligaments provides a data base to evaluate which of the multiplicity of present tendon graft materials has mechanical properties similar to those of the ligaments to be replaced. Those tendon grafts will be the most suitable for replacement of specific ligaments. Finally, data on the mechanical properties of these ligaments offer the possibility for evaluating any future biological or prosthetic grafts.

Aged↗
PubMed1985

Effect of myoelectric signal processing on the relationship between muscle force and processed EMG.

The relationship between the force generated by an isometrically contracting muscle and the associated myoelectric signal has been the subject of extensive investigation in the past and conflicting results were reported regarding this relationship. The objective of the present study was to investigate some of the sources that may lead to such conflicting results. Two possible sources were examined. The first was the variability in the force-EMG relationship resulting from processing the EMG signal with different EMG signal processing techniques and the second was the variability in the force-EMG relation obtained from repeated muscle contractions. The results of the study indicate that slight variations in the force-EMG relationships can be attributed to the selection of different processing techniques. However, the variability in the force-EMG relation, obtained by using different EMG signal processors, was found to be significantly smaller than the variability in this relationship obtained from repeated muscle contractions.

Adult↗
PubMed1984

Passive and active components of the internal moment developed about the ankle joint during human ambulation.

The internal moment developed about a joint during a functional activity is the result of contraction of muscles and the visco-elastic properties of the joint and its surrounding soft tissues. In this study, the contribution of each one of these mechanisms to the total internal moment developed about the ankle joint during human level walking was assessed. The results indicate that during normal level walking the internal moment about the ankle is mainly due to contraction of muscles surrounding the joint. The contribution of the passive component was found to be negligible. These results, however, were found to be different for the pathological case tested. The results indicated that in a subject with a mild equinus ankle deformity, a substantial portion (21%) of the total internal moment was contributed by the passive resistance of the joint and its surrounding structures.

Adult↗
PubMed1982

Simulation of human gait with the aid of a simple mechanical model.

A simple mechanical model was used in this study to simulate the stance phase of human locomotion. The model consists of a concentrated mass supported by two elastic and viscous straight legs. The model is provided with a set of initial conditions at the instant of "heel strike" and then continues to move due to its inertia and the action of gravity. The simulation results were compared with the corresponding experimental data and have shown agreeable similarity. The model was also used to study the effect of some body features on the resulting walking pattern and to explain the generation of the ground reaction force characteristics.

Biomechanical Phenomena↗